This moves them into a new `wasmtime-asm-macros` crate that can be used not just from the `wasmtime-fibers` crate but also from other crates (e.g. we will need them in https://github.com/bytecodealliance/wasmtime/pull/4431).
This moves them into a new `wasmtime-asm-macros` crate that can be used not just from the `wasmtime-fibers` crate but also from other crates (e.g. we will need them in https://github.com/bytecodealliance/wasmtime/pull/4431).